Recently, display devices that control display gray scale of each of a plurality of pixels by use of a thin film transistor (TFT), such as liquid crystal display devices, organic EL (electroluminescence) display devices and the like, have been developed. In such a display device, each of the plurality of the pixels that includes a thin film transistor needs to be supplied with an electric current. For this purpose, the display device includes a terminal unit including a plurality of terminals that are connected to an external circuit or the like and receive the electric current, and a wiring unit including a plurality of lines connected to the plurality of terminals. For such a display device, it is an important issue to prevent deterioration of the terminal unit and the wiring unit to improve the reliability of connection at the terminal unit.
Conventionally in order to realize this, a technology is proposed by which a protrusion is formed in the display device by use of an insulating film in a terminal unit on a substrate including TFTs and the protrusion is used to provide the conduction between the terminal unit and a flexible wiring board (Japanese Laid-Open Patent Publication No. 2008-065135). According to this technology, a thermosetting insulating film is located between a conductive film for terminals that is formed on the protrusion and a bump formed on the flexible wiring board, and the conductive film for terminals and the bump are put into contact with each other via a hole formed in the insulating film, so that the conductance is provided.
However, in the above-described conventional display device, there may possibly be a restriction on the position of the connection part because of the protrusion formed in the terminal unit and the bump formed on an external circuit (flexible wiring board). In this case, the reliability is provided by the insulating film, but the connection resistance may undesirably be high. In addition, since a plurality of minute protrusions need to be formed, the load on the manufacturing process may undesirably be high.